1. Field of the Invention
This invention relates generally to a transport mechanism and, more specifically, to a transport mechanism useful in the high speed manufacture of semiconductor devices.
2. Description of the Prior Art
In the past, semiconductor devices, as for example integrated circuits, have been assembled by various means. The manufacture of such devices requires a handling of the semiconductor chips cut from a wafer at the various stages of detachment from the wafer, inspection, and bonding to a lead frame.
Since the chips range in size from small to minute and are relatively mechanically fragile, a precise, delicate method of locating, picking and moving the semiconductor chips was necessary. Initially, this handling was done manually. Subsequently, various semi-automated and automated apparatus were developed to pick up a semiconductor chip. When removing a chip from the wafer matrix, either the pickup apparatus had to shift to select the next chip or the wafer support had to sequentially position each chip at a pickup point. The release of the chip occurred at a lateral distance from the pickup point at an elevation close to, but not necessarily the same as, the elevation of the pickup point. The actual releasable attachment was accomplished by adhering the chip to a pickup surface with a vacuum. The pickup apparatus was shifted to the respective chips of the wafer grid initially by an adjustable mechanical cam and linkage and, subsequently, by an X-Y transport mechanism driven by electric motors operable at the command of a control apparatus, as for example a computer. This motion was accomplished through the utilization of various mechanical linkages and unidirectionally rotating cams. These devices required substantial set-up time and proved relatively inflexible in that changes, including such minor changes as wafer thickness, required another set-up. Furthermore, such fixed mechanical linkage made no provision for a varying lift which would allow the transported chip to clear vertical obstructions of various heights.
A need existed to provide a semiconductor chip transport apparatus with the capability for rapid adjustment of the vertical and lateral positions of the respective pickup and deposit points.
The semi-automated and automated semiconductor chip transport apparatus in use moved the semiconductor chips through an X-Y-Z coordinate system of the motions thereby necessitating that the chip come to rest in an axial orientation in a horizontal plane such that it was essentially parallel to its pickup position.
A further need existed to provide a semiconductor chip transport apparatus which was capable of picking a semiconductor chip from a wafer and depositing it in a manner such that its X and Y horizontal axes were aligned in a controlled position other than parallel to their original orientation.